Preheat the oven to 375 degrees. Cook the macaroni in a large pot of boiling water until al dente, then drain and set aside.

Steam or boil the broccoli florets for 3 minutes until bright green and slightly tender, then drain and set aside.

In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1 minute to form a roux.

Slowly whisk in the milk, then add the garlic powder, salt, and black pepper. Cook until the sauce thickens, about 3 minutes.

Remove the sauce from heat and stir in 1 1/2 cups of the cheddar cheese until melted.

Combine the cooked macaroni, broccoli, and cheese sauce in the pot or a large bowl. Transfer the mixture to an 8x8 baking dish.

Sprinkle the remaining 1/2 cup cheddar cheese and the panko breadcrumbs evenly over the top.

Bake for 20 minutes until the top is golden and the edges are bubbly. Let it rest 5 minutes before cutting into portions.